Stack chair



FIG. 1 is a perspective view of a single stack chair showing my newdesign;

FIG. 2 is a side elevation view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is top plan view thereof;

FIG. 5 is three-quarter top front view thereof; and,

FIG. 6 is three-quarter top rear view thereof.

CLAIM The ornamental design for a stack chair, as shown and described.